diff --git a/src/mlpack/methods/ann/layer/CMakeLists.txt b/src/mlpack/methods/ann/layer/CMakeLists.txt
index 8c851e0d85..2d15b23661 100644
--- a/src/mlpack/methods/ann/layer/CMakeLists.txt
+++ b/src/mlpack/methods/ann/layer/CMakeLists.txt
@@ -9,8 +9,8 @@ set(SOURCES
   adaptive_max_pooling_impl.hpp
   adaptive_mean_pooling.hpp
   adaptive_mean_pooling_impl.hpp
-  # alpha_dropout.hpp
-  # alpha_dropout_impl.hpp
+  alpha_dropout.hpp
+  alpha_dropout_impl.hpp
   # atrous_convolution.hpp
   # atrous_convolution_impl.hpp
   # base_layer.hpp
diff --git a/src/mlpack/methods/ann/layer/alpha_dropout.hpp b/src/mlpack/methods/ann/layer/alpha_dropout.hpp
index a38e30edea..4b62662b7c 100644
--- a/src/mlpack/methods/ann/layer/alpha_dropout.hpp
+++ b/src/mlpack/methods/ann/layer/alpha_dropout.hpp
@@ -59,6 +59,11 @@ class AlphaDropout : public Layer<InputType, OutputType>
   AlphaDropout(const double ratio = 0.5,
                const double alphaDash = -alpha * lambda);
 
+  /**
+   * Clone the DropoutType object. This handles polymorphism correctly.
+   */
+  AlphaDropout* Clone() const { return new AlphaDropout(*this); }
+
   /**
    * Ordinary feed forward pass of the alpha_dropout layer.
    *
diff --git a/src/mlpack/methods/ann/layer/layer_types.hpp b/src/mlpack/methods/ann/layer/layer_types.hpp
index c7f9fd5b1f..04bf79e40c 100644
--- a/src/mlpack/methods/ann/layer/layer_types.hpp
+++ b/src/mlpack/methods/ann/layer/layer_types.hpp
@@ -20,7 +20,7 @@
 //#include <mlpack/methods/ann/layer/adaptive_mean_pooling.hpp>
 #include <mlpack/methods/ann/layer/add.hpp>
 //#include <mlpack/methods/ann/layer/add_merge.hpp>
-//#include <mlpack/methods/ann/layer/alpha_dropout.hpp>
+#include <mlpack/methods/ann/layer/alpha_dropout.hpp>
 #include <mlpack/methods/ann/layer/base_layer.hpp>
 //#include <mlpack/methods/ann/layer/batch_norm.hpp>
 //#include <mlpack/methods/ann/layer/bilinear_interpolation.hpp>
diff --git a/src/mlpack/tests/ann_layer_test.cpp b/src/mlpack/tests/ann_layer_test.cpp
index a2dcb7cd50..89180483f2 100644
--- a/src/mlpack/tests/ann_layer_test.cpp
+++ b/src/mlpack/tests/ann_layer_test.cpp
@@ -321,96 +321,96 @@ TEST_CASE("NoDropoutTest", "[ANNLayerTest]")
   REQUIRE(arma::accu(output) == arma::accu(input));
 }
 
-// /*
-//  * Perform test to check whether mean and variance remain nearly same
-//  * after AlphaDropout.
-//  */
-// TEST_CASE("SimpleAlphaDropoutLayerTest", "[ANNLayerTest]")
-// {
-//   // Initialize the probability of setting a value to alphaDash.
-//   const double p = 0.2;
+/*
+ * Perform test to check whether mean and variance remain nearly same
+ * after AlphaDropout.
+ */
+TEST_CASE("SimpleAlphaDropoutLayerTest", "[ANNLayerTest]")
+{
+  // Initialize the probability of setting a value to alphaDash.
+  const double p = 0.2;
 
-//   // Initialize the input parameter having a mean nearabout 0
-//   // and variance nearabout 1.
-//   arma::mat input = arma::randn<arma::mat>(1000, 1);
+  // Initialize the input parameter having a mean nearabout 0
+  // and variance nearabout 1.
+  arma::mat input = arma::randn<arma::mat>(1000, 1);
 
-//   AlphaDropout<> module(p);
-//   module.Deterministic() = false;
+  AlphaDropout<> module(p);
+  module.Training() = true;
 
-//   // Test the Forward function when training phase.
-//   arma::mat output;
-//   module.Forward(input, output);
-//   // Check whether mean remains nearly same.
-//   REQUIRE(arma::as_scalar(arma::abs(arma::mean(input) - arma::mean(output))) <=
-//       0.1);
+  // Test the Forward function when training phase.
+  arma::mat output (arma::size(input));
+  module.Forward(input, output);
+  // Check whether mean remains nearly same.
+  REQUIRE(arma::as_scalar(arma::abs(arma::mean(input) - arma::mean(output))) <=
+      0.1);
 
-//   // Check whether variance remains nearly same.
-//   REQUIRE(arma::as_scalar(arma::abs(arma::var(input) - arma::var(output))) <=
-//       0.1);
+  // Check whether variance remains nearly same.
+  REQUIRE(arma::as_scalar(arma::abs(arma::var(input) - arma::var(output))) <=
+      0.1);
 
-//   // Test the Backward function when training phase.
-//   arma::mat delta;
-//   module.Backward(input, input, delta);
-//   REQUIRE(arma::as_scalar(arma::abs(arma::mean(delta) - 0)) <= 0.05);
+  // Test the Backward function when training phase.
+  arma::mat delta;
+  module.Backward(input, input, delta);
+  REQUIRE(arma::as_scalar(arma::abs(arma::mean(delta) - 0)) <= 0.05);
 
-//   // Test the Forward function when testing phase.
-//   module.Deterministic() = true;
-//   module.Forward(input, output);
-//   REQUIRE(arma::accu(input) == arma::accu(output));
-// }
+  // Test the Forward function when testing phase.
+  module.Training() = false;
+  module.Forward(input, output);
+  REQUIRE(arma::accu(input) == arma::accu(output));
+}
 
-// /**
-//  * Perform AlphaDropout x times using ones as input, sum the number of ones
-//  * and validate that the layer is producing approximately the correct number
-//  * of ones.
-//  */
-// TEST_CASE("AlphaDropoutProbabilityTest", "[ANNLayerTest]")
-// {
-//   arma::mat input = arma::ones(1500, 1);
-//   const size_t iterations = 10;
+/**
+ * Perform AlphaDropout x times using ones as input, sum the number of ones
+ * and validate that the layer is producing approximately the correct number
+ * of ones.
+ */
+TEST_CASE("AlphaDropoutProbabilityTest", "[ANNLayerTest]")
+{
+  arma::mat input = arma::ones(1500, 1);
+  const size_t iterations = 10;
 
-//   double probability[5] = { 0.1, 0.3, 0.4, 0.7, 0.8 };
-//   for (size_t trial = 0; trial < 5; ++trial)
-//   {
-//     double nonzeroCount = 0;
-//     for (size_t i = 0; i < iterations; ++i)
-//     {
-//       AlphaDropout<> module(probability[trial]);
-//       module.Deterministic() = false;
+  double probability[5] = { 0.1, 0.3, 0.4, 0.7, 0.8 };
+  for (size_t trial = 0; trial < 5; ++trial)
+  {
+    double nonzeroCount = 0;
+    for (size_t i = 0; i < iterations; ++i)
+    {
+      AlphaDropout<> module(probability[trial]);
+      module.Training() = true;
 
-//       arma::mat output;
-//       module.Forward(input, output);
+      arma::mat output(arma::size(input));
+      module.Forward(input, output);
 
-//       // Return a column vector containing the indices of elements of X
-//       // that are not alphaDash, we just need the number of
-//       // nonAlphaDash values.
-//       arma::uvec nonAlphaDash = arma::find(module.Mask());
-//       nonzeroCount += nonAlphaDash.n_elem;
-//     }
+      // Return a column vector containing the indices of elements of X
+      // that are not alphaDash, we just need the number of
+      // nonAlphaDash values.
+      arma::uvec nonAlphaDash = arma::find(module.Mask());
+      nonzeroCount += nonAlphaDash.n_elem;
+    }
 
-//     const double expected = input.n_elem * (1-probability[trial]) * iterations;
+    const double expected = input.n_elem * (1-probability[trial]) * iterations;
 
-//     const double error = fabs(nonzeroCount - expected) / expected;
+    const double error = fabs(nonzeroCount - expected) / expected;
 
-//     REQUIRE(error <= 0.15);
-//   }
-// }
+    REQUIRE(error <= 0.15);
+  }
+}
 
-// /**
-//  * Perform AlphaDropout with probability 1 - p where p = 0,
-//  * means no AlphaDropout.
-//  */
-// TEST_CASE("NoAlphaDropoutTest", "[ANNLayerTest]")
-// {
-//   arma::mat input = arma::ones(1500, 1);
-//   AlphaDropout<> module(0);
-//   module.Deterministic() = false;
+/**
+ * Perform AlphaDropout with probability 1 - p where p = 0,
+ * means no AlphaDropout.
+ */
+TEST_CASE("NoAlphaDropoutTest", "[ANNLayerTest]")
+{
+  arma::mat input = arma::ones(1500, 1);
+  AlphaDropout<> module(0);
+  module.Training() = false;
 
-//   arma::mat output;
-//   module.Forward(input, output);
+  arma::mat output;
+  module.Forward(input, output);
 
-//   REQUIRE(arma::accu(output) == arma::accu(input));
-// }
+  REQUIRE(arma::accu(output) == arma::accu(input));
+}
 
 // /**
 //  * Simple linear module test.